1. Field of the Invention
The present invention relates to a sensor device including a transducer chip mounted on an island portion (die pad) of a lead frame and a method of producing the sensor device. Further, the present invention relates to the lead frame used for producing the sensor device.
2. Related Arts
Conventionally, acceleration sensor devices using the piezoresistance effect to detect acceleration have an acceleration sensor chip with a detection axis perpendicular to a surface of the sensor chip. The acceleration sensor chip is retained within a package, and the package is mounted on a mounting surface of a circuit board. When there is a need for detecting acceleration in a direction parallel to the mounting surface of the circuit board, the sensor chip retained in the package is disposed on the circuit board such that the surface of the sensor chip becomes perpendicular to the mounting surface of the circuit board.
For example, JP-A-8-320341 discloses this vertical-type acceleration sensor device, in which an acceleration sensor chip is retained in a cavity of a package made of ceramic or resin, and is mounted on the circuit board such that the surface of the sensor chip is perpendicular to the circuit board. In the vertical-type acceleration sensor device, however, the manufacturing cost is high. This is because production of the package requires various processes for forming via holes in the package, filling the via holes with conductive material, printing conductive members for wiring, plating surfaces of the conductive members, and the like.
On the other hand, when producing a horizontal-type of acceleration sensor device in which the acceleration sensor chip is mounted on the circuit board such that the surface of the sensor chip is parallel to the circuit board, there is a low cost method using a lead frame and a resin molded package. Under this method, the acceleration sensor chip is mounted on an island portion of the lead frame, and is molded together with inner leads to form the package. The surface of the sensor chip is always parallel to the surface of the island portion of the lead frame. Therefore, it is difficult for the vertical-type acceleration sensor device to use the lead frame.
When an SIP (Single In-line Package), a ZIP (Zigzag In-line Package), or an SVP (Surface Vertical Package) is adopted as the package for the vertical-type acceleration sensor device, the above-mentioned method can be employed. However, the above-mentioned packages are not sufficiently stable, leading to a possibility that the packages may vary or waver from the initial mounted angle on the circuit board. As a result, reliability of the acceleration sensor device deteriorates.